Standing-seam roofs are widely used in commercial and high-quality residential building construction. Water-tightness of such roofs is ensured by providing standing seams at the edges of the sheet-metal panels, making fastener penetration through the surfaces of the panels unnecessary.
A typical standing-seam roof system includes spaced-apart purlins to secure and support the roof panels, a blanket of insulating material overlaying the purlins, and roof panels overlaying the insulating blanket.
A typical roof panel consists of a generally-flat surface, twelve inches to thirty inches wide, and two upstanding side legs forming a male profile on one side and a female profile on the other side. The panel is typically cold-formed from precoated metal having a thickness ranging from 0.016 inch to 0.05 inch.
The roof surface is typically formed by multiple panels engaged side-by-side and assembled in the following sequence. First, a thermal-insulating blanket is placed over the supporting roof purlins. A panel is then placed in position over the blanket. Clips holding the male-profiled leg of the panel in position are then fastened beside the panel edge to the supporting purlins through the thermal-insulating blanket. Finally, the female-profiled leg of the next panel is placed over the installed clips and caused to mechanically interlock with the male-profiled leg of the installed panel, using either a snap engagement profile design or a joint seaming machine. These steps are repeated until the entire roof area is covered.
Water leakage through the panel surface is prevented by elimination of fastener holes in the panel surface. Water leakage through the seams is prevented by the height of the seam legs and, optionally, a resilient seal along the panel seam.
The clips holding the panels to the supporting purlins are slidably engaged with the panel seams in the longitudinal direction, allowing free thermal movements of the panels and leading to long-lasting seal integrity. The upstanding seam profiles provide bending strength and stiffness against snow load and wind load. Wind uplift load is resisted by the hold-down clips. The interlocked seam provides resistance against separation under loads.
While this prior art system has performed well and met substantial commercial success, there are several drawbacks of the system that could be eliminated. First, the thermal-insulating blanket is compressed by the roof panels at the purlin locations. Blanket compression impairs the thermal efficiency of the insulation and in some cases leads to interior water condensation in cold weather. The compression of the thermal-insulating blanket is magnified by snow load on the roof. Blanket compression can also cause a visible distortion of the flat surface of the roof panel over the purlin locations, resulting in poor appearance.
A second drawback is that the precision-fit seams between roof panels require a close alignment tolerance on the purlins. The required purlin tolerance is not achievable using standard construction techniques. The prior art solution to this problem has been to use shims under the fastening clips; however, due to the compressibility of the thermal-insulating blanket, it is very difficult to predetermine the amount of shimming required before the clips are fastened down. As a result, time-consuming readjustments are often required.
Thus, a need presently exists for a standing-seam roof system which maintains the functional features of the prior art system while eliminating these drawbacks.